Hendra Virus Still Causing Problems in Australia

Hendra Virus Still Causing Problems in Australia

Flying foxes, a type of fruit bat native to Australia, are thought to pass the deadly hendra virus to horses, however the exact mode of transmission remains unclear.

The Australian Veterinary Association (AVA) has reported that 12 horses in Queensland and New South Wales have tested positive for hendra virus since late June. Six facilities in Queensland and three in New South Wales remain under quarantine while veterinarians test the other horses on the properties for the dangerous virus.

Hendra virus has been known to yield numerous clinical signs in horses including respiratory distress, frothy nasal discharge, elevated body temperature (above 40°C, or 104°F), and elevated heart rate; however, authorities caution that hendra infection does not have specific signs.

According to Andrew W. van Eps, BVSc, PhD, MACVSc, Dipl. ACVIM, senior lecturer in Equine Medicine at The University of Queensland School of Veterinary Science, this year has seen an increased number of confirmed hendra cases at separate facilities (rather than one large outbreak in one location, as has occurred in previous years). "From its first identification in 1994 in the suburb of Hendra, Brisbane, Queensland, there had been 14 independent 'outbreaks' of Hendra virus up until this year, and those occurrences have resulted in 45 horse deaths and four human deaths (20 of these horse deaths and two human deaths occurred in the original outbreak in Hendra in 1994," van Eps explained. "The other occurrences have all involved only small numbers of horses each time and often only single horses. This year so far in Queensland, there have been six separate 'outbreaks' with eight horses dead since June."

Van Eps explained that hendra virus is prevalent in the flying fox (a type of fruit bat found in Australia) population, and researchers believe horses contract the virus from these bats. The exact method of transmission, however, remains unclear.

"It is not known exactly how the bats transmit the virus to horses, but (the virus) is present in the urine, feces, and placenta/placental fluids of bats," van Eps said. "It is thought that these materials are dropped onto areas where horses are feeding or drinking (thus transmitting the virus to the horse)."

Although the definitive reason behind the hike in confirmed cases remains unknown, van Eps noted that some believe the devastating flooding and cyclones that hit Australia earlier in the year could have played a role: "The severe flooding and cyclones that occurred in Queensland earlier in 2011 might have altered or destroyed some fruit bat habitats and resulted in them being stressed, which in turn has resulted in more shedding of hendra virus by the bats, and possibly some altered distribution of colonies.

"Also, due to the markedly increased awareness amongst the public and veterinarians, many more horses are being tested than was the case previously," he added. "This means that cases that might have gone undiagnosed in the past are now being identified."

So is there anything that can be done to control virus spread? While van Eps noted that there is a possibility the virus could spread to such states as Victoria and further throughout New South Wales, the spread is largely dependent on the bat population.

"There have been calls from the industry to cull or eradicate bats, but this is unlikely to help and may in fact stress existing populations, leading to increased shedding and transmission," he explained. "The bats are also an important part of the ecosystem in Australia."

The AVA recently issued a statement indicating that eradicating the bats in hopes of controlling virus spread could only make matters worse.

"Calls to eradicate flying foxes in an attempt to control hendra virus are ignoring the facts," Barry Smyth, BVSc, FACVSc, Dipl. ACVS, president of the AVA, said in the statement. "They fly and travel long distances and would be very difficult if not possible to eradicate.

"We understand people's anxiety about this virus," he continued. "Vets who see sick horses every day are really in the firing line of the disease, and the number and range of cases this year is certainly alarming. Our best option for dealing with this deadly disease is the hendra horse vaccine currently in development. We're looking forward to the vaccine being available as soon as humanly possible."

Earlier this year Australian researchers announced that a hendra virus vaccine is nearing completion, and it could be available to consumers within a few years if final testing is successful.

In the statement Smyth acknowledged that the virus is more widespread than usual this year, and that it should be considered a national problem: "With the unprecedented number of cases across a vast area this year, it's clearly a national and urgent problem. Both flying foxes and horses travel large distances in Australia, and we believe all horses will need to be vaccinated to adequately protect against the disease. We think that vaccination should be a condition of entry into events, races, and shows."

About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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